Download Chapter 10

What are you most scared of?
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Fireworks discharge
Lightning
Gunshot
Earthquake
Car accident
Your chance of dying from . . .
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Fireworks discharge – 1 in 386,766
Lightning – 1 in 84, 079
Gunshot – 1 in 6,309
Earthquake – 1 in 148,756
Car accident – 1 in 66
Statistics from National Safety Council
Chapter 10: Risk, Toxicology,
& Human Health
What is risk?

Risk – possibility
of suffering harm
from a hazard
Impacts of risks on humans





Mortality
Morbidity
Loss of quality of life
Loss of work days
Property damage
Examples of Cultural Hazards
Smoking
 Poor Diet
 Poverty
 Unsafe sex

Examples of Chemical Hazards
Air
 Water
 Soil
 Food

Examples of Physical Hazards
Fires
 Earthquakes
 Volcanic eruptions
 Floods
 Tornadoes
 Hurricanes

Examples of Biological Hazards
Pathogens
 Pollen
 Allergens
 Animals

Quantitative Measures of Risk

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Probabilities - a
mathematical
statement about the
likelihood of harm
Can be expressed in
three ways:

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
1:100
1/100
“One in one hundred”
Quantitative Measures of Risk


Ex: 1:6,210 - risk of dying from alcohol
 (1 person in 6,210 people will die of alcohol
related illness)
The bigger the bottom number (denominator)
the less the chance
 Ex: chance of winning Power Ball lottery:
about 1 in 80,000,000
 Ex: chance of laughing at with Mr. Strogen
today: about 1 in 3
Toxicology

Dose – the amount of a substance that a
person has in their body
 Can be:
• Ingested
• Inhaled
• Injected
• Absorbed
 “The
dose makes the poison”
Sensitivity to Toxins


The amount of
damage
(response) is
related to the
dose you get
Response is
related to age,
gender, and
genetic makeup
Toxicology
Solubility - what can the chemical
dissolve in?
 Water-soluble toxins
 Oil/Fat-soluble toxins
 Which do you think is generally “better” for
the health of an organism?
 Water is “better” since it can be diluted
 Fats aren’t good since chemicals can
gather in body fat of animals

Toxicology

Persistence - how long a chemical stays in the
environment
 Roundup (kills plants) breaks down in 24 hours
when exposed to light
 DDT (kills insects) breaks down in 2 to 15 years
Toxicology


Bioaccumulation
 chemicals
stored in
organs (fat) of
animals
Biomagnification
 chemicals are
passed to each
member of the
food chain
 large amounts
in animals at
top of chain
Interactions

Synergistic interactions: when two (or more)
risk factors have a greater effect together than
each by themselves

Ex: being exposed to asbestos and smoking gives
you a 400 times greater chance of developing lung
cancer than if you experienced only one of those risks
+
=
Interactions

Antagonistic interactions: an exposure of two
(or more) chemicals results in a reduction in the
effect compared to when taken individually

Ex: mercury toxicity can be reduced by consuming
the chemical dimercaprol
+
=
Toxicity Assessment
An interesting animal study concerning the artificial
sweetener saccharin

Animal studies indicated that saccharine caused
bladder cancer in animals. In 1977, the FDA proposed
a ban on its use.

Studies later reveled that the doses given to animals
were the equivalent of a human drinking 100 cans of
soda a day. Human tests never linked saccharine to
human cancer because the way that saccharine
caused cancer to rats does not happen in humans.

Saccharine was taken off the FDA’s possible cancer
list in 2000, after 25 years of needless worry.

Worry is still around today.
Toxicity Assessment

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Poisons – materials that kill at a very small
dose (50 milligrams or less per kilogram of
weight)
The LD50 (lethal dose) is the amount that
kills 50% of a test population in a given time
Toxicity Assessment
•The LD50 of this
chemical is 7
•The dose that
kills 50% is the
LD50
LD50
LD50 = 5.3
STEPS TO MEASURE RISK
Toxicity Ratings
Toxicity
Rating
super toxic
LD50
< 0.01
extremely
toxic
< 5
very toxic
5–50
toxic
50–500
moderately
toxic
500–5,000
slightly toxic
essentially
nontoxic
5,000–15,000
> 15,000
Average Lethal
Dose
less than 1 drop
Exam ples
nerve gases, botulism,
mushroom toxins, dioxin
less than 7 drops potassium cyanide, heroin,
atropine, parathion,
nicotine
7 drop to 1
mercury salts, morphine,
teaspoon
codeine
1 teaspoon to 1
lead salts, DDT, sodium
ounce
hydroxide, fluoride, sulfuric
acid, caffeine, carbon
tetrachloride
1 ounce to 1 pint methyl alcohol, ether,
pehobarbital,
amphetamines, kerosine,
aspirin
1 pint to 1 quart ethyl alcohol, lysol, soaps
more than 1 quart water, glycerin, table sugar
Threshold
% Mortality
Effects of KCl on Daphnia
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
Concentration (mg/L)
5
5.5
6
6.5
7
Case Study – DDT
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Dichlorodiphenyltrichloro
ethane
Used as an insecticide
beginning in the 1940s,
primarily in tropical areas
of the world with malaria
and typhus
Highly effective at killing
insects
USNAS estimates that
DDT saved 500 million
lives
• In 2010, malaria killed 655,000 people
• There are currently 216 million people infected
• Every minute, an African child dies of malaria
Case Study – DDT

1962, Rachel Carson wrote Silent Spring,
which described the negative effects of
pesticides, like DDT:
Cancer in humans
 Thinner egg shells, reproductive problems,
and death in birds

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Carson was concerned with the
widespread spraying of chemicals,
especially since we didn’t fully understand
its effects on the environment or humans
Case Study – DDT

Silent Spring resulted in a public
outcry to ban DDT
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1972, banned in the US
2004, banned worldwide (some
exemptions)
Often cited as the beginning of the
“environmental movement”
DDT Discussion

How much do you agree with the
following statement?
Despite its usefulness at preventing
diseases like malaria (and saving
millions of lives each year), DDT should
be banned worldwide because of its
negative environmental and health
effects.
Chemical Risks

Neurotoxins:
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Carcinogens:
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chemicals that interfere with the normal development
of embryos and fetuses
Allergens:
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chemicals that cause cancer
Teratogens:
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chemicals that disrupt the nervous system
chemicals that cause allergic reactions
Endocrine disruptors:

chemicals that interfere with the normal functioning
of hormones
Risk Assessment vs. Risk Management

Risk Assessment
“What is the hazard?”

Risk Management
“How can the risk be
minimized?”
Risk Analysis
Qualitative vs. Quantitative
• Qualitative risk assessment: judging
the relative risk of various decisions (ex:
low, medium, or high)
• Judgments based on perception, not
on actual data
• Quantitative risk assessment:
determining the probability of an event
occurring using data (ex: 83% chance)
Probabilities of Death in U.S.
Risk Analysis
Probability of being exposed to a hazard
Risk =
x
Probability of being harmed if exposed
Risk Analysis

What is riskier: flying on a plane for 1,000 miles
per year or eating 40 tablespoons of peanut
butter per year?

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The probability of a plane crash is low, but the
probability of dying if the plane crashes is high
The probability of eating peanut butter is high, but
the probability of developing cancer from the peanut
butter is low
Both behaviors produce a risk of 1 in 1 million
Chemical Regulation